The Art of System Equalization Dave Swallow

In this section, we’ll look at the actual process of equalization, and we make the assumption that you have a system GEQ and a rack-mountable GEQ. On small PA systems you will probably only have GEQ, but you will find that bigger systems have a GEQ at FOH that you can adjust, and also a system GEQ incorporated into the crossovers. These types of GEQs are only accessed by either a computer or a button pressing combination on the front of the crossover. You might find some kind of computer screen that is connected to the crossover, so the system tech or in-house engineer can set the system up the way they want it, and then all the other engineers who come in and out of the venue use the graphic at FOH. A lot of the time you’ll find that the system EQ curve is locked, whereas other times the in-house engineers are happy to turn it off. Remember that, when you’re in this situation, you’re in danger of double EQing.

Graphic EQ is used to tune the frequency response of the speaker to the room so that it sounds accurate or hi-fi for all sound sources. Desk EQ is used as a creative production tool to alter the tonal balance of each individual instrument and vocals.

When EQing, look at where you’re positioned and how that will affect the sound, as well as where the audience will be. The biggest thing to remember at this point is that you are just looking to remove any anomalie, that is, any frequency or frequencies that stand out more than they should. Remember, though, that when EQing the loudspeakers, you’re creating phase and frequency shifts over the entire mix. Applying a 400-Hz cut over the whole system means that all your instruments will be cut at 400 Hz. If the tone from your bass guitar comes from there, or that is where one of your toms is tuned to, you’ll have to boost those frequencies to bring that out again. Changing the phase over the whole mix could be a potentially bad thing because your audio ends up sounding like it’s “tiny” rather than being wide and open. Individually, though, EQ changes on the channels can and will enhance the mix. The following question arises: Is there too much frequency emphasis in the room or in the mix? You need to really listen to what you’re doing. Trial and error helps, but experience is the best teacher. Once you understand the listening part, everything else is fairly natural.

As you’re listening to your music through the PA, before you touch any form of EQ, you need to get out from behind the mixing console and go for a walk. There might be frequencies that are more prominent in other parts of the venue than others, and you also need to listen to how the rest of the venue sounds in relation to where you are. Keep in mind the differences between where you are and the rest of the venue. If you stand in the middle of the room and it sounds great, then leave it; most of the audience will be standing there. You’re listening for frequencies that jump out at you; these will present themselves as kind of loud notes being played. You’re also listening for frequencies that you should hear; this is why you need a track that you know well. What you’re listening for translates to all EQ, and it too comes down to personal taste. Once you’ve decided which frequencies are sticking out, head over to your GEQ and remove them. One thing to keep in mind while going through this process is that not all PAs can reproduce everything equally well. If you are listening for some subtle percussion in the music you are playing and it seems to be stuck very far in the back ground, you might try and EQ so that it stands out a bit more. You are in danger here of adding too much EQ that could swamp the rest of the mix. Listen to how those frequencies sit in the room, and your mix, but make a mental note of what you have done and review it later.

Don’t try and do much EQing on the main system EQ. The room will respond differently when there are people there, so understand what you’re pulling out. If you end up pulling out a lot of highs, be aware that you might have to push them back in later on. It’s far easier to do this on a graphic than it is on the EQ hidden away within the crossover, using a computer screen and magic pen that moves things around.

As a touring engineer, I’ve never been afraid of getting my hands dirty with a graphic. Once, at the House of Blues in Houston, I raised the faders up on the CD I was using to EQ the system, and I heard what can only be described as a bloody awful sound coming out of the speakers. I turned the CD down, checked that the EQ wasn’t in on the channel, no high pass (HP) or low pass (LP) filters were in, checked the gain, and even checked the CD through the headphones to make sure the sound was good on my end. When I couldn’t figure out what was wrong, I asked the in-house engineer, and I was informed that the system always sounded like this. To try and fix it, I played around with the graphic. When I got something that was at least remotely close to what I wanted (“remotely” being the key word), the screen looked like I’d been playing a game of Battleship. I asked if this was a typical EQ curve for engineers to put on the system, and his response was: “I’ve seen some pretty extreme EQs in here.” The system was installed by a PA company, and then the in-house guys were locked out of any proper control over the system. The system probably would have been set up with the standard factory settings, and placed in the room when no one was in there. It would have then had a general system EQ placed over the whole thing, the crossover points set, and would have been locked and left for the in-house techs to get along with. This meant that they couldn’t improve on the sound as more and more shows were coming through—which means if that is an engineer’s first experience of an Adamson PA, he’ll never want to use it again.

The point is that sometimes systems just sound bad, so don’t be afraid to jump in and push around a few GEQ faders to get the sound you want. Because of the way the graphics are split up, you only have 1/3 octave steps (1/3 octave bandwidth for each fader), so don’t be surprised if you end up cutting one frequency and boosting the next to try and find an in-between. It’s not the most efficient way of doing things, but sometimes you can get the sound you need, and as with anything in live audio, there is always a compromise.

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